Added the ability to add statement 'exceptions' to the grunt task

### CHANGE SUMMARY
* Added exceptions option, you can specify statements to ignore in validation (xit, xdescribe), etc.
* Added that and and example of an options config to the README.md file.

I also realize this is very similar to a recent Pull Request, but this takes a slightly different direction, and it appears that one was never merged in. Regardless, however you want to go, please advise.